Xerographic fusing apparatus



April 27, 1965 "r. c. MURRAY ETAL 3,180,971

XEROGRAPHIC FUSING APPARATUS- Filed Oct. 1, 1962 3 Sheets-Sheet l INVENTOR. THOMAS C. MURRAY BY ROBERT A. SCHAEFFER zw fi/M A T TORNEV April 1965 T. c. MURRAY ETAL 3,180,971

EROGRAPHIC FUSI Filed Oct. 1, 1962 3 Sheets-Sheet 2 I :2 so

3i FIG. 2

THOMAS c. MURRAY BY OBERT A. SCHAEFFER A TTO EX April 27, 1965 Filed 001.. 1, 1962 T. C. MURRAY ETAL XEROGRAPHIC FUSING APPARATUS .5 Sheets-Sheet 3 INVENTOR. THOMAS C. MURRAY ROBERT A. SCHAEFFER A T TOR/VIE Y United States Patent Ofiiice 3,136,971 Patented Apr. 27 1965 3,180,971 XEROGRAPIHC FUSING APPARATUS Thomas C. Murray and Robert A. Schaetfer, Rochester, N .Y., assignors to Xerox Corporation, Rochester, N.Y., a corporation of New Yorlr Filed Oct. 1, 1962, Ser. No. 227,472 3 Claims. (Cl. 219216) This invention relates to improvements in fusing apparatus and particularly to fusing devices for permanently bonding xerographic powder images to paper and to either paper or metal lithographic masters.

More specifically, the invention relates to an improved fusing device that will accept a sheet of material with an image to be fused, and, after a predetermined length of time, eject the sheet of material with the image bonded thereon. Although the invention is considered to have general application wherever material of any type must be heated to a required temperature for a specific length of time, it is particularly useful in the field of xerography and has an important application in the fusing of resinous powder images deposited on sheets of paper, or the like, and retained'thereon by electrostatic latent charge. Therefore, for convenience of illustration, the invention is described with reference to its use as a heat fuser for xerographic powder images. However, it is to be understood that it may be employed with equal facility in other fields.

In the xerographic process, a light image of the copy being reproduced is flashed onto the electrostatically charged surface of a xerographic plate. The plate comprises a layer of photoconductive insulating material on a conductive backing. The area of the plate exposed to light, discharges the electrostatic charge leaving a latent electrostatic charge opposite to that of the plate. The plate is then exposed to a toner material containing an electrostatic chcarge opposite to that of the plate. The toner material adheres to the plate in the areas containing the electrostatic charge, thus producing a powder image of the copy being reproduced. This powder image is then transferred to a support material, such as paper or a lithographic master. The process of exposing and developing the xerographic plate is more fully described in the copending application S.N. 227,340, filed October 1, 1962. The process of transferring the powder image from the plate surface to a sheet of support material is described in the copending application of S.N. 234,686, filed November 1, 1962. For the purposes of this application, it is sutlicient to note that the image is transferred by placing a sheet of support material in contact with the powder image on the plate surface and charging the surface with an electrostatic charge of the same polarity as the original charge on the plate surface. When the support material is removed from the plate surface, the powder image adheres thereto by means of the electrostatic charge.

The basic process of xerography is described in Carlson Patent 2,297,691, issued October 6, 1942. It is noted in the Carlson patent that a variety of types of finely divided electroscopic powders may be employed for developing electrostatic latent images. However, as the art of xerography has progressed it has been found preferable to develop line copy images with a powder or toner formed of any of a variety of pigmented thermoplastic resins that have been specifically developed for the purpose. These resinous powders are specifically compounded for producing dense images of high resolution and to have characteristics permitting convenient storage and handling. Such developing materials are compounded to permit them to be fixed or bonded to the surface of a transfer material either by heat fusing or vapor fusing techniques, in accordance with the particular application in which they are employed. The individual particles of resin soften and coalesce when heated or plasticized by solvent, so that they become sticky and readily adhere to the surface of the transfer material.

In order to fuse resinous powder images, it is necessary to heat the powder, and the paper to which it is to be fused, to a relatively high temperature. The temperature must be kept fairly constant, if the temperature fluctuates too low or the time that the support material is exposed to the temperature is too short, the resinous powder will not properly adhere to the support surface; and if the temperature is too high or the time of exposure too long, there is a tendency for the support material to discolor or scorch.

Existing commercial fusing equipment usually consists of either an oven where the support material is placed on a plate and is inserted into the oven and manually withdrawn after a predetermined length of time, or as in automatic xerographic reproducing machines, the support material is carried on a belt or conveyor mechanism past a heat fuser at a predetermined rate. The present invention encompasses an oven wherein the support material may be inserted into the oven and will automatically be ejected at the proper time. There is no requirement of an automatic conveyor or any manual timing process by the operator.

It is therefore the primary object of this invention to improve apparatus used to bond resinous powder images to a support material surface.

It is a further object of this invention to improve heat fusing apparatus so that a sheet of material containing a resinous powder image may be inserted into an oven by an operator and be automatically ejected without any further act on the part of the operator.

It is a further object of this invention to provide a heating oven wherein the material heated in the oven is ejected at the termination of a predetermined length of time.

It is a further object of this invention to provide heat fusing apparatus that permits insertion of the material to be fused into an oven without being deflected by escaping Warm air.

It is a further object of this invention to provide heat fusing apparatus with an inclined heating chamber that does not lose appreciable amounts of warm air when material is inserted into the chamber.

These and other objects of the invention are attained by means of an oven containing an entrance door which when opened sets an automatic timer. The material to be fused is inserted into said oven and the timing device opens means provided at the opposite end of the oven to permit the material to pass by gravity through an exit opening. An entrance door and an exit door are provided so that one door is closed at all times preventing a rush of warm air out the entrance opening when material is being inserted.

The invention is disclosed in the appended drawings, in which:

FIG. 1 is an isometric view of a preferred embodiment of the present invention;

FIG. 2 is a detailedplanned view of the present invention with parts broken away to show the internal structure of the heat fuser;

FIG. 3 is a detailed sectional view taken along line 33 of FIG. 2.

For the purpose of illustration, the heat fuser described herein is shown, as in FIG. 1, as a table top or desk-type heat fuser. Although size is not a limitation, the preferred embodiment shown in FIG. 1 is capable of receiving any standard size sheet of paper and paper or metal lithographic masters. The heat fuser, generally designated 1, is supported by a support stand 2, mounted a on a desk or table 3. The fuser l is generally of box-like configuration and mounted on support stand 2 at an angle of approximately 50 degrees with the horizontal.

The fuser 1 consists of a receiving door 4 mounted in the elevated end of the fuser, and a discharge door 5 switch 13, an indicator light 14, a calibrated timer dial 15, and a thermostat dial 16.

The support stand 2, may be of any convenient type of stand to support the fuser at the appropriate angle. The stand shown herein consists of metal rods bent in. a manner to support the fuser in the desired position, and is integral with a metal basket 17 located beneath the discharge door 5 so as to receive the material ejected from the fuser. 7

Referring now to FIGS. 2 and 3, there is shown the internal structure of the fuser wherein a passageway 18, referred to herein as the fusing chamber, extends through the fuser from receiving door 4 to discharge door 5. Fusing chamber 18 extends substantially across the width of the fuser and is enclosed by a fiat stainless steelpiate 19 on the bottom and sides, and on the top by an alumi' num plate 2%), Mounted on the top of plate 26 are a plurality of heating elements 21. Heating elements 21 are located in chamber 22 and are fastened to the aluminum plate Ztl by means of bolts 23. These heating elements may be of any conventional design such as resistance coils or as shown herein, commercially obtainable ring heaters, and are approximately positioned on plate 2% to provide a uniform temperature level throughout chamber 13. Heating elements 21 and chamber 22 are separated from top panel 112 by means of transit sheet 24 and air space 25. The fuser bottom panel 8 is separated from the fusing chamber 18 by air space 26. Air spaces 25 and 26 may be filled with any suitable bulktype insulation, such as fiber glass or, as shown herein, by a reflective insulation, such as aluminum foil at. The size of air spaces 25 and 2d and the type and amount of insulation provided therein is determined by the operating temperatures of heating elements 21 and chamber 18, so that the temperature of panels 12 and 8, do not exceed a safe working temperature. The amount of insulation used in chamber 25 may be reduced or the temperature in chamber 22 may be increased without producing an unsafe condition merely by using a protective shield over panel 12. End panels 9 and 19, side panel ill and interior wall 27 are also suitably insulated to retain the heat in chamber 18 and to maintain the temperature of the exterior portion of the heat fuser at a safe working level.

A compartment 28 is provided between the exterior side cover 11 and the interior wall 27. The compartment 2% contains the body of heat switch 13, controlling heater elements 21 and indicator light 14, which provides a visual indication that the heater elements are operating. The temperature in chamber 13 is controlled by means of thermostat 29 operatively connected to control the heat output of elements 21. Thermostat 29 has a thermostat expansion bulb 30 located in chamber 22 and held in intimate contact with aluminum plate Ztl by means of brackets 32. The expansion of volatile fluid in bulb St? is relayed .to thermostat 29 through tubing 31, and I thermostat 29 is set to respond to any desired temperature by means of thermostat dial 1o. Dial 116 is shown herein as located on the exterior surface of side panel 11, however, it may be desirable in certain installations to locate thermostat dial if within compartment 28, thus preventing the possibility of accidentally increasing the temperature inchamber 18. For most operations, it will be found desirableto, pro-set the temperature dial lo and vary the time which material is left in chamber 1%, rather than varying the temperature of chamber 1%. l The door handle 7 is mounted in bearing member 33 which in turn is rigidly mounted on the interior side of wall 11.. On one end of handle '7, located in compartment 28, is a collar 36 containing a lever arm 34 and secured to the end of handle 7 by means of a pin or set screw 35. The lever arm 34 is pivotably connected to a bar or rod 37 by means of pin 38, and to a' tension spring 39, which is coupledtobracketdl mounted on wall ill. The bar member 37 is pivotably connected to receiving door 4 by means of pin 42 so that movement of handle 7 in a downward direction, as seen in FIG. 1, produces an angular movement of lever arm 34 which is transmitted through bar member 37 and pin 42 to receiving door 4. Receiving door 4 pivots in a downward direction about hinge assembly 43.

The movement of receiving door 4 is transmitted through rod 45 to the discharge door 5. Rod 45 is pivotably connected to bracket as which is fastened to discharge door 5. Discharge doorS pivots in a downward direction about two hinge assemblies 44 positioned on each side of door 5. Hinge assembly 2- consists of a brace 65 fastened to the bottom cover 8 and a bracket 6e connectedto door 5. Bracket as is rotatably attached to brace as by pin 67. Receiving door 4 normally is in a closed position and discharge door 5 is normally in an open position, both as seen in PEG. 3. The discharge door and receiving door cannot be open at the same time. If both doors were open at the same time. warm air in chamber 13 would rise upward and out of top opening in chamber 18, thus producing a movement of air at the receiving end of chamber 18 that would interfere with the paper or support material being inserted therein. The support material is commonly quite flexible and as one end is being inserted into chamber 13, the draft arising out of the chamber would tend to deflect the end of the support material, making the actual insertion quite difiicult. Therefore, as receiving door 4 is opened, discharge door 5 is closed, preventing any how of air through the fuser. After handle '7 is released from its down position, it is returned to its original position by means of spring 39 fastened to lever arm 34. At the handle're turns to its normal position, receiving door 4- is closed and discharge door 5 is opened.

The paper or support material 47 located in chamber 118 is retained therein by means of a series of wire fingers 48 mounted on a shaft 49 and passing through openings 5% in plate 19. The shaft 49 is mounted on a bracket 51 fastened to the underside of plate 19. The fingers 48 are bent at right angles, as seen in FIG. 3, with one side of the angle passing upward through openings to a position near or in contact with plate Zll. As support material 47 is placed in chamber 18, there is occasionally a tendency for the support material to hug the top of chamber 18 and'tend to ride over the top of fingers 48. To prevent this from occurring, a series of small indentations 52 have been made in the top of plate 20 along a path parallel to and just in front of fingers 48. The indentations in plate 2% result in a series of projections, in chamber 18 that will deflect the paper or support material downward onto fingers 48. Alternatively, a series of small holes could be provided in the top plate fid'to accommodate the fingers 48 thus eliminating any gap between the top of the finger member and the top plate.

The shaft @9, holding fingers 48, contains a crank arm 53 which is connected to mechanism timer 54 through linkage 55. The timer 54 is operated by a lever arm 57 mounted on the timer shaft, and is connected to the lever arm 34 of the door handle 7, by means of a flexible wire member ill, a tension spring 59 and a connecting rod 58. As the handle 7 is rotated, the movement is transmitted from the lever arm 34, to lever arm 57, through the intermediate linkage, and produces a rotational movement. The rota-.

tional movement of lever 57 winds and sets the timer 54, which in turn, after the lapse of the predetermined time, activates linkage 55 and crank 53 causing rotation of shaft 49. As the shaft 49 is rotated, the fingers 48 are Withdrawn from chamber 18, permitting the support material 47 to pass under its own weight out of chamber 18 into basket 17 When the receiving door is again opened, the timer mechanism is rewound and fingers 48 are moved through openings 50 into chamber 18, The linkage system shown for rotating lever 57 is one embodiment of many possible variations. For example, if a larger rotational movement is desired to produce a greater winding and a longer time interval for timer 54, then a flexible member may be attached from lever arm 34 to a rotatable drum in place of lever 57, and wrapped around the drum so that movement of handle 7 would produce an unwinding of the flexible member from the drum, producing the desired degree of rotation. In this method, the degree of rotation is determined by the length of lever arm 34 and the angular movement of handle 7. The timer 54, shown herein, is a conventional mechanical timer with a 01 minute time interval.

In operation, the heating elements 21 are energized through switch 13 and the desired temperature of chamber 18 is set on thermostat dial 16. After a lapse of time to allow chamber 18 to reach operating temperature, usually -15 minutes, and the amount of time that the support material is to remain in chamber 18 is set on timer dial 15, the handle 7 is rotated in a clockwise direction as seen in FIG. 1, setting timer 54 and opening receiving door 4 and closing discharge door 5. Support material 47, containing a resinous powder image, is inserted through the fuser opening at the receiving door 4 into chamber 18 and is retained therein by means of fingers 48. The handle 7 is released, spring 39 returns it to its normal position and closes receiving door 4 and opens discharge door 5. At the termination of the time lapse set on timer dial 15, the timer 54 actuates linkage 55 and crank arm 53 rotating shaft 49, thus pulling fingers 48 through openings 50 into chamber 26. The support material 47 is no longer retained by fingers 48 and passes under its own weight through the exit opening into basket 17. The resinous powder image contained on the support material 47 has been tackified and bonded to the support material producing a permanent image thereon. This operation may be repeated for subsequent sheets of support material.

Although the invention is described herein as used for bonding resinous powder images to a support material surface, it will be apparent to those skilled in this or re- 7 lated arts, that it may readily be applied to any system in which it is required to heat material to a predetermined temperature for a predetermined length of time. Therefore, since changes could be made in the above construction, and different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the specification and drawings be interpreted as illustrative and not in a limiting sense.

What is claimed is: 1. Apparatus for fusing xerographic powder images to a support material surface including:

an inclined heating chamber with an opening in the upper and lower ends and inclined at an angle to the horizontal sufficient to permit a sheet of support material inserted in the opening at the upper end to be gravity fed through the chamber and out the opening at the lower end,

means to heat the chamber to a temperature sufi'icient to fuse a xerographic powder image to a sheet of support material and including means to control the temperature of the chamber,

a plurality of finger-like elements supported on a movable member adjacent the heating chamber and extending into the chamber and traverse the path of movement of a sheet of support material through the chamber,

an automatic timing device operatively connected to the movable member to withdraw the finger-like extensions from the path of movement of the support materminal after a predetermined time interval,

and means to initiate operation of the automatic timing device prior to insertion of a sheet of support material into the heating chamber.

2. Apparatus for fusing xerographic powder images to a support material surface including:

an inclined heating chamber with an opening in the upper and lower ends and inclined at an angle to the horizontal sufficient to permit a sheet of support material inserted in the opening at the upper end to be gravity fed through the chamber and out the opening at the lower end,

means toheat the chamber to a temperature suificient to fuse a xerographic powder image to a sheet of support material and including means to control the temperature of the chamber,

a normally closed entrance door operatively associated with the opening in the upper end of the heating chamber,

means to open said door for the insertion of a sheet of support material into the heating chamber,

retaining means mounted in said chamber to hold a sheet of support material in the chamber during fusing of the pwder image,

an automatic timing device operatively connected to the retaining means to release the support material for continued passage through the chamber after a predetermined time interval,

and a linkage member connected between the entrance door and the automatic timing device to initiate operation of the timing device upon the opening of the entrance door.

3. The apparatus of claim 2 also including:

a normally opened exit door operatively associated with the opening at the lower end of the heating chamber and including a linkage member connected between the entrance door and the exit door to close the exit door upon opening of the entrance door thereby minimizing the loss of heat from the heating chamber when the entrance door is open.

References Cited by the Examiner UNITED STATES PATENTS 2,899,202 8/59 Mestre 271-53 2,933,979 4/60 Lacoe 219201 X 2,965,266 12/60 Rutcus et al. 222-70 3,064,959 11/62 Eisenberg et al 219214 X 3,076,083 1/ 63 Codichini et al 2l9-216 65 RICHARD M. WOOD, Primary Examiner, 

1. APPARATUS FOR FUSING XEROGRAPHIC POWDER IMAGES TO A SUPPORT MATERIAL SURFACE INCLUDING: AN INCLINED HEATING CHAMBER WITH AN OPENING IN THE UPPER AND LOWER ENDS AND INCLINED AT AN ANGLE TO THE HORIZONTAL SUFFICIENT TO PERMIT A SHEET OF SUPPORT MATERIAL INSERTED IN THE OPENING AT THE UPPER END TO BE GRAVITY FED THROUGH THE CHAMBER AND OUT THE OPENING AT THE LOWER END, MEANS TO HEAT THE CHAMBER TO A TEMPERATURE SUFFICIENT TO FUSE A XEROGRAPHIC POWDER IMAGE TO A SHEET OF SUPPORT MATERIAL AND INCLUDING MEANS TO CONTROL THE TEMPERATURE OF THE CHAMBER, A PLURALITY OF FINGER-LIKE ELEMENTS SUPPORTED ON A MOVABLE MEMBER ADJACENT THE HEATING CHAMBER AND EXTENDING INTO THE CHAMBER AND TRANSVERSE THE PATH OF MOVEMENT OF A SHEET OF SUPPORT MATERIAL THROUGH THE CHAMBER, AN AUTOMATIC TIMING DEVICE OPERATIVELY CONNECTED TO THE MOVABLE MEMBER TO WITHDRAW THE FINGER-LIKE EXTENSIONS FROM THE PATH OF MOVEMENT OF THE SUPPORT MATERMINAL AFTER A PREDETERMINED TIME INTERVAL, 